Drive System For Electrically Operated Vehicle

ABSTRACT

A drive system is provided for a utility vehicle and includes an alternating-current (AC) motor for providing a drive torque. An AC motor controller receives a battery voltage signal, throttle pedal position signal, brake pedal position signal, key switch signal, forward/neutral/reverse (FNR) signal, and run/tow signal indicative of the utility vehicle being configured to be driven and being configured to be towed. The AC motor controller generates an AC drive signal for the AC motor, wherein the AC drive signal is based on the battery voltage signal, throttle pedal position signal, brake pedal position signal, key switch signal, FNR signal, and run/tow signal.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/896,967 filed Oct. 4, 2010 as a continuation of U.S. patentapplication Ser. No. 12/487,695 filed on Jun. 19, 2009 as a continuationof U.S. patent application Ser. No. 11/966,289 filed on Dec. 28, 2007 asa continuation of U.S. patent application Ser. No. 11/260,867 filed onOct. 27, 2005. This application claims the benefit of U.S. ProvisionalApplication No. 60/623,149, filed on Oct. 28, 2004. The specificationsof the above application are incorporated herein by reference in theirentirety.

FIELD

The present disclosure relates generally to a brushless, alternatingcurrent (AC) drive system for providing motive power to drive wheels ofan electrically operated vehicle.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

All electric motors, such as alternating current (AC) motors or directcurrent (DC) function on a principle that two magnetic fields inproximity to one another have a tendency to align. One way to induce amagnetic field is to pass current through a coil of wire. If two coilswith current passing through them are in proximity to each other, therespective magnetic fields that are generated have a tendency to alignthemselves. If the two coils are between 0 and 180 degrees out ofalignment, this tendency may create a torque between the two coils. Anarrangement where one of these coils is mechanically fixed to a shaftand the other is fixed to an outer housing is known as an electricmotor. The torque produced between these coils may vary with the currentthrough the coils.

AC motors may encompass a wide class of motors, includingsingle/multiphase, universal, servo, induction, synchronous, and gearmotor types, for example. The magnetic field generated by AC motors maybe produced by an electromagnet powered by the same AC voltage as themotor coil. The coils that produce the magnetic field are traditionallycalled the “field coils” while the coils and the solid core that rotatesis called the armature coils.

AC motors may have some advantages over DC motors. Some types of DCmotors include a device known as a commutator. The commutator ensuresthat there is always an angle between the two coils, so as to continueto produce torque as the motor shaft rotates through in excess of 180degrees. The commutator disconnects the current from the armature coil,and reconnects it to a second armature coil before the angle between thearmature coil and field coil connected to a motor housing reaches zero.

The ends of each of the armature coils may have contact surfaces knownas commutator bars. Contacts made of carbon, called brushes, are fixedto the motor housing. A DC motor with a commutator and brushes may beknown as a ‘brushed’ DC motor, for example. As the DC motor shaftrotates, the brushes lose contact with one set of bars and make contactwith the next set of bars. This process maintains a relatively constantangle between the armature coil and the field coil, which in turnmaintains a constant torque throughout the DC motor's rotation.

Some types of AC motors, known as brushless AC motors, do not usebrushes or commutator bars. Brushed DC motors typically are subject toperiodic maintenance to inspect and replace worn brushes and to removecarbon dust, which represents a potential sparking hazard, from variousmotor surfaces. Accordingly, use of a brushless AC motor instead of thebrushed DC motor may eliminate problems related to maintenance and wear,and may also eliminate the problem of dangerous sparking. AC motors mayalso be well suited for constant-speed applications. This is because,unlike a DC motor, motor speed in an AC motor is determined by thefrequency of the AC voltage applied to the motor terminals.

There are two distinct types of AC motors, AC synchronous motors and ACinduction motors. A synchronous motor consists of a series of windingsin the stator section with a simple rotating area. A current is passedthrough the coil, generating torque on the coil. Since the current isalternating, the motor typically runs smoothly in accordance with thefrequency of the sine wave. This allows for constant, unvarying speedfrom no load to full load with no slip.

AC induction motors are generally the more common of the two AC motortypes. AC induction motors use electric current to induce rotation inthe coils, rather than supplying the rotation directly. Additionally, ACinduction motors use shorted wire loops on a rotating armature andobtain the motor torque from currents induced in these loops by thechanging magnetic fields produced in the field coils.

Conventional electric motor driven vehicles such as golf cars and smallutility vehicles are DC powered, and primarily powered by a shunt-typeDC drive system. The shunt-type DC motor has replaced many of the olderseries wound DC motors for powering vehicles such as golf cars. Ashunt-type DC motor has armature and field windings connected inparallel to a common voltage source, a configuration which offersgreater flexibility in controlling motor performance than series woundDC motors. However, these shunt type motors still present maintenanceand potential spark hazard problems. It is not heretofore believed thata brushless AC drive system has been developed which provides the motiveforce for driving wheels of a vehicle such as a golf car.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.Throughout the disclosure, like elements are represented by likereference numerals, which are given by way of illustration only and thusare not limitative of the various embodiments.

FIG. 1 is a block diagram an AC drive system in accordance with variousembodiments.

FIG. 2 is a block diagram of an instrument panel in accordance with anvarious embodiments.

FIG. 3 is a block diagram illustrating an arrangement of CANcommunication chips in accordance with various embodiments.

FIG. 4 is a block diagram illustrating a front wheel speed sensor inaccordance with various embodiments.

FIG. 5 is a block diagram illustrating a multiple or all wheel drivearrangement in accordance with various embodiments.

DETAILED DESCRIPTION

FIG. 1 is an exemplary block diagram of an AC drive system in accordancewith various embodiments. In FIG. 1, there is shown an AC drive system100, which may include a three-phase (3φ) AC motor 110, such as aninduction motor or permanent magnet motor, and a matched AC drive motorcontroller 120 to be used in conjunction with an electrically operatedvehicle 190 such as a golf car and/or a small utility vehicle. As willbe described in more detail below, AC drive system 100 may providetractive power, service brake functionality, and recovery and conversionof kinetic energy from vehicle 190 motion to potential energy in theform of electromotive force (EMF).

Referring to FIG. 1, in response to motor controller 120, motor 110 mayprovide motive force to drive wheels 198 imparting motive force ortractive energy via axle 192 through locking differential 194 and shafts196 to rear wheels 198. Motor 110 may be operatively connected to anelectrically actuated brake 180 under the control of motor controller120 via signal line 185 and/or motor 110. Additionally, throttle controlfor a throttle (accelerator pedal) 170 may be provided via a throttleposition sensor 175 and a throttle enable sensor 177, based on signalsreceived over lines 126 from motor controller 120. Further, AC drivesystem 100 may include a service brake pedal 160 to operatively controlbraking by motor 110 in accordance with signals from motor controller120. Movement of service brake pedal 160 is detected by one or both ofsensors which generate control signals sent to motor controller 120 viacommunication lines 122. Sensors associated with brake pedal 160 mayinclude a brake position sensor 163 and a full stroke sensor 165, to bedescribed in further detail below.

Motor controller 120 may be in operative communication with one or moreof a portable battery pack 130, charger 140, an external network 150,and other external devices or outputs 155 such as a reverse alarm sensorvia a direct connection or a controller area network (CAN) bus 145 andassociated connector interfaces, as shown in FIG. 1. Operative controland data exchange between motor controller 120, charger 140 and externalnetwork 150 are described in further detail below.

The AC system logic for AC drive system 100 may include a series ofdrive inputs and drive outputs. The following describes exemplary inputsto and outputs from the system logic as implemented in intelligentdevices such as motor controller 120. It will be understood by oneskilled in the art that input and output parameters or signals otherthan described below may be implemented with the exemplary AC drivesystem.

FIG. 2 is a block diagram of an exemplary instrument panel in accordancewith various embodiments. Referring to FIG. 2, a suitable instrumentpanel 200 may include a key switch 220, forward, neutral and reverse(FNR) switch 230, low battery indicator 235, amp-hour meter 240, LED245, controller indicator 248, and reverse alarm indicator 250.Controller indicator 248 may indicate a condition, such as normalstatus, warning, and the like, for AC controller 120 or other componentsof the AC motor control system. LED 245 may be embodied as a single LEDor multiple LEDs and may be configured to display suitable numeric oralphanumeric error codes. The error codes may include, but are notlimited to error codes related approaching threshold or warningconditions of AC motor 110, motor controller 120, battery pack 130,service brake pedal 160, electrically actuated brake 180, or the like.

Vehicle 190 may also include a suitable run/tow switch 210 provided at adesired location for actuation by an operator of vehicle 190. Therun/tow switch 210 may be located on the vehicle 190 at a place that isconvenient for towing, yet a location where the switch may not be easilyactivated from the operator's (or passenger's) position, so as to avoida purposefully or inadvertently cycling of switch 210 during normaldriving evolutions of the vehicle 190.

When the run/tow switch 210 is selected to RUN, motive power may beprovided via motor controller 120 and motor 110 to drive vehicle 190.When the run/tow switch 210 is switched to TOW, the electric brake 180may be de-energized for a time period sufficient to actuate electricbrake 180 and motor controller 120, such as one (1) second, and mayapply a given pulse width modulated (PWM) percentage, such as a 40% byway of example hold on the electric brake 180 thereafter. As will bedescribed in greater detail herein, this may allow the vehicle 190 to betowed at speeds up to or slightly above rated motor speed, which may beapproximately 4650 RPM for an exemplary golf car application. With therun/tow switch 210 in TOW, a towing mode may be enabled that provideszero wheel torque.

Another input to the system logic may be provided via a key switch 220having ON/OFF switch positions. With the key switch 220 set to the ONposition, drive logic power may be enabled to motor controller 120 andpower may be enabled to the electric brake 180. Setting the key switch220 to OFF position may disable the logic power to the motor controller120 and de-energize the electric brake 180.

Actuation of the FNR switch 230 to FWD may enable drive logic power forselecting a forward drive direction. Forward speed may be up to ratedmotor speed, or a vehicle speed in accordance with the rated motorspeed. Actuation of the FNR switch 230 to NEUTRAL may disable drivelogic power for selecting either a forward drive direction or reversedrive direction, so as to place AC motor 110 in a free-wheeling mode ata relatively constant RPM (i.e., idle). Actuation of the FNR switch 230to REV may enable drive logic power for selecting a reverse drivedirection. This switch position may optionally sound a reverse alarm.Reverse direction speed may be desirably limited to less than the ratedspeed, such as 60% of maximum motor speed, or a vehicle speed ofapproximately 10 MPH.

Another drive input to the system logic may include a throttle positionsensor 175, as shown in FIG. 1. The throttle position sensor 175 may belocated in signal line 126 between the accelerator pedal or throttle 170and motor controller 120 and may be configured to output an analogvoltage that may be converted to a digital signal in the A/D converterof controller 120. The voltage may vary between about 0 to 5.0 volts inaccordance with the position or depression of throttle 170. In anexemplary configuration, 0-0.5 volts may indicate a 0 RPM commandedspeed and 4.5 volts or greater may indicate a maximum commanded motorspeed In other words, a 0.5 volt output corresponds to 0% commandedmotor speed or zero RPM. A 4.5 or greater volt output corresponds to100% commanded motor speed in the forward direction (4650 RPM) andapproximately 60% commanded motor speed in the reverse direction (2790RPM). The throttle position sensor 175 may be embodied as a suitablepotentiometer or Hall Effect sensor, and may thus provide a limitationon actual speed to 100% of motor speed in either the forward or reversedirections.

Another drive input to the system logic may be via throttle enablesensor 177. The throttle enable sensor 177, also occasionally referredto as a pedal-up sensor, may sense one of a drive mode and a pedal-upmode, based on the position of the accelerator pedal or throttle 170.When sensing the drive mode (at any point the pedal is depressed) thethrottle enable sensor 177 energizes a main contactor to enableoperation of AC motor 110 and to energize the electric brake 180 so asto enable drive power, via motor controller 120 and motor 110, to wheels198. If the pedal-up mode is sensed (indicating that the acceleratorpedal is fully ‘up’ and not depressed, the main contactor may bede-energized to disable drive.

Accordingly, exemplary input conditions that may be met to providemotive power to wheels 198 could include the key switch 220 placed in ONand the FNR switch 230 selected to either the FWD or REV position, therun/tow switch 210 selected to RUN, brake position sensor 163 receivinga 0% braking command from motor controller 120, and a battery 130 stateof charge (SOC) of at least 20%. These are merely exemplary conditionsto provide motive power, other conditions may be set within the ordinaryskill of the art.

Another drive input to system logic may be provided via brake positionsensor 163. Similar to the throttle position sensor 175, the brakeposition sensor 163 is located in a signal line 122 between the brakepedal 160 and motor controller 120 and outputs an analog value (voltage)that is converted to a digital signal in the A/D converter of motorcontroller 120. For example, sensing of less than 0.5 volt output frombrake position sensor 163 may represent 0% braking and the enabling ofmotive power to the wheels 198. Between 0.51 to 1.0 volts output, actualspeed may be maintained via regenerative braking and no motive power maybe applied to wheels 198, for example. Between 1.01 to 4.0 volt output,a proportional deceleration speed ramp may increase with increasinginput voltage. The start and finish conditions may be adjustable, forexample. For a 4.1 to 4.5 or greater volt output from brake positionsensor 163, commanded motor speed may be 0% and the electric brake 180may be de-energized (such as via a control signal sent by motorcontroller 120 over signal line 185, as shown in FIG. 1, for example) toenable electric brake 180 to apply a braking torque or braking pressureupon motor 110. The braking function may be tunable in accordance withcourse conditions, such as wet, dry, hilly, and flat terrain, andvehicle performance to provide a consistent feel to the brakingoperation.

The logic functions of the brake position sensor 163 may override andmaintain priority over any throttle input to throttle 170, for example.The logic function for the brake position sensor 163 may operate withthe key switch 220 to ON, the FNR switch 230 to either FWD or REV, andthe run/tow switch 210 in either RUN or TOW, the throttle enable sensor177 sensing either drive mode or pedal-up mode and the throttle positionsensor 175 sensing commanded motor speed anywhere between 0 to 100%. Afurther condition may be any battery SOC value above 0%.

Another input to the system logic may be battery voltage. Motorcontroller 120 may monitor the battery pack 130 voltage under load ormay monitor the internal resistance (impedance) of the battery pack 130in order to determine the battery pack 130 state of charge (SOC). Withthe SOC between about 100% to 25%, controller 120 may enable motivepower to drive the vehicle 190. With an SOC between about 24% and 20%,the logic in motor controller 120 may limit commanded speed to 40%maximum drive speed, or approximately 1860 RPM, or approximately 6 MPHto provide a limp-home capability. For a SOC less than 20%, no motivepower is supplied to power vehicle 190. The logic may thus limitcommanded speed to zero RPM, the electric brake 180 may be de-energized,and motor braking via motor 110 may be enabled to protect battery pack130 from being too deeply discharged. The electric brake 180 may beenergized by the run/tow switch being selected to TOW at this latter SOCrange.

Table 1 summarizes exemplary drive inputs to the logic of motorcontroller 120.

TABLE 1 Drive Inputs Input Position Function Run/Tow Switch 210 Run Mustbe selected to enable motive power to drive the vehicle. Tow EnergizesElectric brake 180 for 1 second and then applies 40% PWM hold onelectric brake 180 thereafter. Allows the vehicle 190 to be towed atspeeds up to and slightly above rated motor speed. (4650 rpm). Towingmode provides zero wheel torque. Towing occurs multiple times daily.External switching of the U, V, or W power wires is not required. Keyswitch 220 ON Enables drive logic power to motor ON/OFF controller 120and energizes electric brake 180 OFF Disables logic power to the motorcontroller 120. De-energizes the electric brake 180. Throttle EnableDRIVE Energizes main contactor. De- Sensor 177 energizes the electricbrake 180. Enables drive. PEDAL-UP De-energizes the main contactor.Disables drive. Throttle Position 0.5 V input 0% commanded motor speed(0 rpm) sensor 175 4.5 V input 100% commanded motor speed (4650 rpm) FWDand (2790 rpm) REV Limit actual speed to 100% motor speed (4650 rpm) FWDand REV Other input conditions that may be met to provide motive power:Key switch 220 = ON and FNR switch = FWD or REV Run/Tow switch 210 = RunBrake position sensor 163 = 0% braking command Battery SOC > 20% Brakeposition 0.5 V input 0% braking, motive power is enabled. sensor 1630.51 V-1.0 V Maintain actual speed via input regenerative braking—nomotive power. 1.01 V-4.0 V Proportional deceleration speed ramp inputincreases with increased input voltage (start and finish slope isadjustable). 4.01 V-4.5 V Commanded motor speed is 0% input (0 rpm)De-energize[[s]] the electric brake. This logic function has priorityover throttle input. Operates in the following conditions: Key switch =ON and FNR switch = FWD or REV Run/Tow switch 210 = Run or Tow Throttleenable switch 177 = ENABLE or DISABLE Throttle position sensor 175 = 0%to 100% Battery SOC > 0% Battery Voltage Monitor the battery pack 130voltage under load or the internal resistance of the battery pack 130 todetermine the battery pack State of Charge (SOC) SOC = 100% to enablesmotive power to drive vehicle 25% - 190 SOC = 24% to Limits commandedspeed to 40% 20% maximum speed drive. (1860 rpm) SOC = 19% to Limitscommanded speed to 0% (0 rpm). 0% Electric brake 180 is De-energized.Motor braking is enabled. Electric brake 180 can be energized only byRUN/TOW switch 210 = TOW. Electric brake has a manual override tomechanically release spring. FNR SWITCH 230 FWD Enables drive logicpower and (FWD/NEUTRAL/REV) selects forward drive direction. Forwardspeed is 100% of maximum motor speed. (4650 rpm) NEUTRAL Disables logicpower to the motor controller 120. De-energizes the electric brake 180.REV Enables drive logic power and selects reverse drive direction. Soundreverse alarm 250. Reverse direction speed is 60% maximum motor speed.(2790 rpm).

AC drive system 100 may include several exemplary drive outputsgenerated by motor controller 120. For example, a reverse alarm outputmay be generated by controller 120 to activate the reverse alarm 250when the key switch 220 is in RUN and the FNR switch 230 is in REV, andthe run/tow switch 210 is selected to RUN, for example. Motor controller120 may disable the reverse alarm 250 when the key switch 220 isselected to ON or when the run/tow switch 210 is selected to TOW.

Drive output logic may be provided to the electric brake 180. Driveoutput logic of motor controller 120 may enable electric brake 180 to amaximum activation voltage, such as 48 volts, for one second and thendrop to 40% PWM thereafter when the run/tow switch is selected to TOW,or when the key switch 220 is selected to ON, the FNR switch 230 to FWDor REV, and throttle enable sensor 177 is in a drive mode, and actualmotor speed is 0 RPM, for example. These are only exemplary conditions,other conditions may be applicable within the ordinary skill of the art.

AC drive system 100 may provide drive output logic to control the maincontactor. Drive output logic may enable the main contactor at aselected maximum voltage, such as 36 volts (or other voltages), for onesecond and then drop to 40% PWM thereafter when the run/tow switch 210is selected to TOW, or when the run/tow switch 210 is selected to RUN,the key switch 220 is ON and FNR switch 230, selected to FWD or REV, andthe throttle enable sensor 177 is in drive mode. Controller 120 maydisable the main contactor at 0 volts when the RUN/TOW switch 210 isselected to RUN and the key switch 220 is selected to OFF, FNR switch230 is FWD or REV and the throttle enable sensor 177 position is in adrive mode, for example.

Drive output logic may also be provided for controlling the lockingdifferential 194. Logic may enable the locking differential 194 toengage at a selected maximum voltage such as 12 volts, for example, forone second and then drop to 40% PWM, or other selected intermediatevoltage, thereafter. Conditions for engaging locking differential 194may be satisfied if the RUN/TOW switch 210 is selected to RUN, or if thekey switch 220 is selected to ON and FNR switch 230 to FWD and REV, andthe throttle enable sensor 177 is in drive mode and actual motor speedis greater than 0 RPM, for example. Drive output logic may disable thelocking differential 194 at 0 volts, if the run/tow switch 210 isselected to TOW and the key switch 220 is selected to OFF, or if the keyswitch 220 is selected to ON, the FNR switch 230 to FWD or REV, thethrottle enable sensor 177 is in pedal-up mode and actual motor speed is0 RPM, for example. These are merely exemplary conditions toengage/disengage the locking differential 194, other conditions may beset within the ordinary skill of the art.

Table 2 summarizes the drive outputs from the logic of motor controller120.

TABLE 2 Drive Outputs Output Position Function Reverse Enabled 12 V whenKey switch 220 = ON, FNR Alarm 250 switch 230 = REV and when RUN/TOWswitch 210 = RUN Disabled 0 V when Key switch 220 = ON, FNR switch 230 =FWD or REV or when RUN/TOW switch 210 = TOW Electric Enabled 48 V for 1second and then drop to 40% Brake 180 PWM thereafter when RUN/TOW switch210 = TOW or Key switch 220 = ON and FNR switch 230 = FWD or REV andThrottle enable sensor 177 = drive, or actual motor speed > 0 rpm) MainEnabled 36 V for 1 second and then drop to 40% Contactor PWM thereafterwhen RUN/TOW switch 210 = TOW or RUN/TOW switch 210 = RUN and Key switch220 = ON, FNR switch = FWD or REV and throttle enable sensor 177 =drive. Disabled 0 V when RUN/TOW 210 = RUN and Key switch 220 = OFF orRUN/TOW 210 = RUN and Key switch 220 = ON, FNR switch 230 = FWD or REVand throttle enable sensor 177 = pedal-up. Locking Enabled 12 V for 1second and then drop to 40% Differential PWM thereafter when RUN/TOW =TOW or Key switch = FWD or REV and (Throttle enable sensor 177 = driveor actual motor speed > 0 rpm) Disabled 0 V when (RUN/TOW 210 = RUN andKey switch 220 = OFF) or Key switch = ON, FNR switch 230 = FWD or REVand throttle enable sensor 177 = pedal- up and actual motor speed = 0%(0 rpm)

Communication between intelligent devices such as the motor controller120, battery pack 130, charger 140, external network 150 and varioussensors and actuators such as throttle 170, electric brake 180, servicebrake pedal 160, etc. may be provided via controller area network CANbus 145 and associated CAN connector interfaces. For example, a CAN chipwith high, low, and ground pins may be provided in a suitable driveconnector at the motor controller 120. As will be described in furtherdetail below, communication protocol may be a suitable CAN protocol suchas CAN open 2.0B or compatible protocol. The CAN bus interfaces withinAC drive system 100 may provide an intermittent diagnostic ability viaexternal network 150 as well as communication with charger 140, forexample. Data may be exchanged between the various components of the ACdrive system 100 and stored within motor controller 120. Such data mayinclude, but is not limited to, drive errors, warnings and fault codes,battery state of charge, battery voltage, number of charge cycles,amount of run times and charge, total drive time and total logic powertime, for example. Although a CAN bus has been described as an exemplarybus architecture, the exemplary embodiments may employ alternative busarchitectures. Other suitable bus architectures may include, but are notnecessarily limited to: RS 232, RS 422, USB, serial, parallel, wireless,Bluetooth and/or optical buses, for example.

AC Motor

Referring again to FIG. 1, motor 110 may be configured as a three-phase,four-pole, AC motor, such as an induction motor or permanent magnetmotor. Such motors may be brushless. Internally, motor 110 may include awound stator and a permanent magnet rotor. Having the windings in thestator may help to efficiently dissipate winding heat. The statorwindings may be connected in a three-phase wye configuration, forexample, here shown as the three drive phases U, V and W (embodied aswires U, V and W in FIG. 1). The rotor may consist of a shaft and a corewith rare earth permanent magnets, its circumference providing inherentlow inertia.

In general, rotor motion may be started by generating a revolvingmagnetic field in the stator windings which interacts with permanentmagnet fields in the rotor. The revolving field may be created bysequentially energizing winding phase pairs of the three drive phases U,V and W. The winding phase pairs may be energized with current flow in agiven sequence to produce the desired direction of rotation. At anyinstant, two of the three phases may be energized while the third phaseis off. Energizing two phases simultaneously combines the torque outputof both phases.

The AC drive system 100 may run off of a DC voltage source, for example,but has a slightly more complicated commutation logic than a brushlessDC drive system. In the AC drive system 100, the power to each phase maybe turned on and off gradually by using pulse width modulation (PWM).

In general, PWM is modulation in which a duration of pulses is varied inaccordance with some characteristic of the modulating signal. As anexample, a pulsing semiconductor or pulse width modulator such as a FET(commonly used in the electronics industry) may create a desired voltagethat is proportional to the duty cycle, and which causes power to agiven phase to be turned on or off. Alternatively, pulse frequencymodulation could be used to create this desired voltage. In either case,the FET may be switched between the ON and OFF states to create adesired voltage that is proportional to the duty cycle at which it isswitched.

Use of an AC motor 110 in vehicle 190 may provide a motor that requiresless maintenance, has a substantially long life, low EMI, andsubstantially quiet operation. An AC motor such as the illustrativemotor 110 may produce more output power per frame size than PM orshunt-type DC motors and gear motors. The low rotor inertia of motor 110may provide improved acceleration and deceleration times whileshortening operating cycles, and the linear speed/torque characteristicsof brushless AC motors such as motor 110 may produce predictable speedregulation. Further, with brushless AC motors the need for brushinspection is eliminated, making them ideal candidates for limitedaccess areas such as a golf car and applications where servicing may bedifficult.

Motor Controller

Motor controller 120 may be embodied in hardware and/or software as oneor more digital microprocessors that may be provided on a printedcircuit card, for example. However, instead of a digital microprocessor,motor controller 120 may be embodied as an analog processor, digitalsignal processor and/or one or more application specific integratedcircuits controlled by a suitable microcontroller or microprocessor (notshown).

Controller Area Network (CAN)

A controller area network (CAN) is a high-integrity serial datacommunications bus for real-time applications. A CAN may operate at datarates of up to 1 Megabits per second (Mbps) and has excellent errordetection and confinement capabilities. CANs may be typically used inautomotive control applications, industrial automation and controlapplications, for example.

Referring to FIG. 1, CAN bus 145 may be a serial bus system especiallysuited for networking intelligent devices such as motor controller 120,as well as sensors and actuators within system 100, although other busarchitectures may be suitable as previously described above. In general,a CAN bus is a serial bus system with multi-master capabilities, thatis, all CAN nodes may be able to transmit data and several CAN nodes maysimultaneously request the CAN bus 145. The serial bus system withreal-time capabilities is the subject of the ISO 11898 internationalstandard and covers the lowest two layers of the ISO/OSI referencemodel. In controller area networks, there is no addressing ofsubscribers or stations in the conventional sense, but instead,prioritized messages may be transmitted.

In general, a transmitter in a CAN may send a message to all CAN nodes.Each node may decide, on the basis of a received identifier, whether itshould process the message or not. The identifier may also determine thepriority that the message enjoys in competition for CAN bus 145 access.The relative simplicity of the CAN protocol may mean lower cost, CANchip interfaces make applications programming relatively simple.

The CAN chips envisioned for AC drive system 100 may be commerciallyavailable, low-cost controller chips. Such controller chips mayimplement the CAN data link layer protocol in a suitable material suchas silicon and may be configured for simple connection tomicrocontrollers such as motor controller 120 or to a suitablecontroller of charger 140, for example.

A feature of the CAN protocol is its high transmission reliability. ACAN controller, which may be suitably embodied as a chip on anintegrated circuit board with motor controller 120, for example,registers station errors and evaluates the errors statistically in orderto take appropriate measures. These measures may extend to disconnectinga given CAN node that is the source of the errors, for example. Further,each CAN message may transmit from 0 to 8 bytes of information. Ofcourse, longer data information may be transmitted by usingsegmentation, as is known. The maximum transmission rate specified inISO11898 is 1 Mbit/s. This data rate applies to networks up to 40meters. For longer distances, the data rate may be reduced; for example,for distances up to 500 m, a speed of about 125 kbit/s is possible, andfor transmissions up to 1 km a data rate of at least about 50 kbit/s ispossible.

FIG. 3 is a block diagram illustrating an arrangement of CANcommunication chips in accordance with various embodiments. Referring toFIG. 3, a suitable CAN communication chip 310 may be installed in themotor drive at either the motor 110 or motor controller 120 on vehicle190. A second CAN communication chip 320 may be installed in the charger140, which may be typically mounted in the vehicle recharge area, suchas where vehicles are parked during down-time or at night, and connectedto a 110 V outlet. A DC charger plug 330 may be connected to the chargerreceptacle 340 of vehicle 190 for recharging the battery pack 130 asneeded, which may be nightly for example. One or more of a DC chargercable 350, plug 330 vehicle charger receptacle 340 and a vehicle wireharness (not shown) for vehicle 190 may contain a dedicated CAN high,low and in-ground signal wires. When connected for charging, theseconnections may thus form the CAN bus 145 that links the motorcontroller 120 to the charger 140 and other intelligent devices for dataexchange, for example.

As discussed above, motor controller 120 may record and storeinformation in a suitable memory or storage as the vehicle 190 is used.Examples of a built-in memory medium may include, but are not limitedto, rewritable non-volatile memories, such as ROMs, flash memories, andhard disks. Examples of removable storage media may include, but are notlimited to, optical storage media such as CD-ROMs and DVDs,magneto-optical storage media, such as MOs, magnetism storage media suchas floppy disks, cassette tapes and removable hard disks, media with abuilt-in rewritable non-volatile memory such as memory cards, and mediawith a built-in ROM, such as ROM cassettes for example.

Typical data stored in the associated memory or storage of the motorcontroller 120 for later exchange with the charger 140 may include, butare not limited to, drive time in forward, drive time in reverse, logictime on (i.e., KEY ON time for key switch 220, the time that logic poweris applied to motor controller 120), various warnings, conditions andfaults, the battery pack 130 SOC, amp-hours consumed and voltage data,and data to assist in operating charger 140. The communication dataexchange over CAN bus 145 may be bi-directional, i.e., the charger 140may also send data to the motor controller 120. This functionality mayprovide a means to change parameters of an entire vehicle fleet whichwould enable optional services purchased for an entire vehicle fleet forany number of single cars vehicles 190 in the fleet.

Any number of chargers 140 may be connected to form a larger controllerarea network, for example. Any CAN-supportable external network 150 suchas a Dongle, a laptop computer, a handheld computer or server may alsobe connected to the CAN bus 145 to provide a system where data exchangebetween the remote CAN-supported computer and any vehicle 190 in thefleet may be made, for example. Accordingly, bi-directional dataexchange via CAN bus 145 may provide an ability to rotate a vehiclefleet to maintain even vehicle 190 usage, and/or may provide an abilityto warranty the vehicle 190 based on usage (i.e., hours, mileage) forexample. Further, bi-directional data exchange via CAN bus 145 mayprovide an ability to predict service needs and to collect data oncourse use, duty cycle, thermal cycles, driving styles, etc.

Battery pack 130 may include a plurality of battery cells connected inseries (i.e., a 48Vdc electric power via four serially-connected 12Vdcbatteries to power vehicle 190. Pack 130 may be embodied as any of alithium ion (Li+), nickel cadmium (NiCd), nickel metal hydride (NiMH),or lead-acid battery pack, for example, in terms of the chemistry makeupof individual cells, electrodes and electrolyte of the pack 130.

In other various embodiments, motor controller 120 may be configured todetermine an ideal amount of power to return to the vehicle's batterypack 130 by monitoring the energy applied to the motor 110 duringvehicle 190 operation since the last charge cycle, in order to determinethe state of charge (SOC) for the battery pack 130, as a percentagevalue. Based on the SOC, the motor controller 120 may provide data tocharger 140 so charger 140 can return energy to battery pack 130 inaccordance with or in proportion to the SOC when the charger 140 isoperatively connected to the vehicle 190.

For example, the motor controller 120 may sum the amount of energyconsumed during operation of the vehicle 190 since the last known chargecycle. The energy removed may be subtracted from a given last knowncharge cycle, thereby determining a battery pack 130 state of charge(SOC). A given amount of energy equal to a ratio of energy removed toenergy returned to the battery pack 130 may be calculated by suitablesoftware within motor controller 120 or another intelligent device, suchas charger 140. This ratio may be optimized in relationship to theamount of drive system efficiencies, battery pack type, battery package, and the rate of energy consumption, for example, although otherparameters may be used for optimization of the ratio of energy removedto energy returned to the battery pack 130. This may be proportional tothe internal resistance of battery pack 130.

Another aspect of the exemplary embodiments may be directed to anelectrically actuated brake 180, also occasionally referred to herein asa parking brake 180 or an electric brake 180 and which is configured toapply a braking torque or braking pressure to motor 110. Parking brake180 may be actuated when the brake pedal 160 of the vehicle 190 is at amaximum stroke. The brake 180 may be a brake by wire design that mayinclude a brake pedal position sensor 163 and brake full stroke sensor165, as shown in FIG. 1, each configured to provide an analog signalinput to controller 120 over signal line 122 that is converted to adigital signal in the A/D converter of the motor controller 120, aspreviously described. Accordingly, electric brake 180 can be actuated bythe motor controller 120 based on either or both of the brake pedalposition sensor 163 and brake full stroke sensor 165 inputs.

Referring to FIG. 1, and during normal driving situations, the electricbrake 180 may be powered to a released position by the motor controller120. Brake pedal sensor 163 determines the position of brake pedal 160to vary the electrical energy applied to electric brake 180 by providingan input to motor controller 120 via signal line 122 which, based on theinput, sends a digital command such as a brake control signal toelectric brake 180 over signal line 185, as shown in FIG. 1. When brakepedal 160 is depressed to within about 5% of the maximum brake pedalstroke as indicated by brake full stroke sensor 165 (analog signal)input, for example, power to electric brake 180 may be directlyinterrupted (i.e., controller 120 is bypassed) to effect a parking oremergency brake function. Once this circuit is open, power is removedfrom the electric brake 180 and a friction material is spring applied tothe disk. The springs of electric brake 180 are sized to apply apressure to the friction material, providing a braking torque equal toor greater than about 120% of the motor 110 maximum dynamic torque. Thisaction reduces the motor speed toward zero until the vehicle 190 reacheszero speed, or until the brake full stroke sensor 165 is deactivated,i.e., when the user releases the brake pedal 160 greater than apredetermined distance from its full stroke or fully applied position,such as the aforementioned 5% of the maximum brake pedal stroke by wayof example. As an alternative, motor controller 120 can utilize thebrake full stroke sensor 165 independently of the brake pedal sensor 163to apply electric brake 180 and initiate a parking brake function usingonly that input. The system may further be configured so that activatingthe brake pedal 160 at zero speed releases the electric brake 180 andholds vehicle 190 stationary. At any time where the pedal 160 isreleased, which deactivates the brake full stroke sensor 165, normallycommanded vehicle driving may resume.

The brake pedal position sensor 163 may be used for service braking bycommanding a given motor speed reduction per unit time. The position ofbrake pedal 160 as sensed by brake pedal sensor 163 provides an input tomotor controller 120 to determine the deceleration rate of vehicle 190.The electrically operated brake 180 may be a motor shaft mounted, springapplied and electrically released disc brake, for example. The electricbrake, 180 may also assist on down-hill braking.

In accordance with the position of brake pedal 160, the brake pedalposition sensor 163 may send the motor controller 120 a signal to reducethe motor speed and induce a braking torque that is proportional to thepedal position. The braking torque may be minimal with minimal brakepedal 160 depression, and may be at a maximum at the full brake pedal160 depression, for example.

The brake full stroke sensor 165 may complement, but would not replacean emergency stop, which may be activated by turning the key switch 220to the off position, thereby positively stopping the vehicle 190. Thebrake full stroke sensor 165 may thus function as redundant safetyswitch, and may be provided to maintain a safe driving condition wherethe vehicle 190 is stopped in a panic or unforeseen single emergencyevent. Such an event can include interruption of operation of motorcontroller 120, failure, operator error and/or other external events,for example.

In another aspect, motor controller 120 may be configured to provide anautomatic park braking function. In order for the motor controller 120to determine when to automatically engage the parking brake 180, themotor controller 120 may monitor the motor commanded speed, actualspeed, key switch position, throttle and brake conditions, for example.

There may be several possible conditions that could cause the motorcontroller 120 to automatically engage the parking brake 180. Forexample, one condition may occur when the vehicle 190 is coasting,without any command from either the accelerator (throttle 170) or thebrake pedal 160. For this condition to exist, the vehicle 190 is moving,and the key switch 220 is selected to ON and the FNR switch 230 is inFWD position. Based on these input conditions, motor controller 120 mayreduce the motor speed by a given amount per unit time, which may bereferred to as “neutral braking.” If vehicle 190 remains in thiscondition, and the actual motor speed is within a given range near zerospeed, motor controller 120 may remove power from the electric brake 180and the parking brake 180 may be commanded to be set. After a giventime, the motor controller 120 may disable the motor 110. If the motorcontroller 120 detects actual motor speed above the given range nearzero speed, motor controller 120 may attempt to prevent the motor 110from rotating, maintaining the vehicle 190 at a stop.

Another condition may occur if the brake pedal 160 is depressed asufficient time to bring the vehicle 190 to a complete stop, then theparking brake 180 is engaged. A complete stop may be defined as a givenrange of speed near zero speed, for example. For this condition toexist, the vehicle 190 may be commanded to a stop by depressing thebrake pedal 160, the key switch 220 is ON, and the commanded speed andactual speed are at 0 RPM or within the given speed range near zerospeed. Based on these inputs, motor controller 120 may command theelectric brake 180 to engage. After a given time has elapsed, motorcontroller 120 may disable the motor 110. If the motor controller 120detects that actual motor speed above the given range near zero speed,motor controller 120 may attempt to prevent motor 110 from rotating,maintaining the vehicle 190 at a stop.

Another condition may occur if any error in the logic inputs to AC drivesystem 100 exist, if a sensor is out of range, or if the motorcontroller 120 faults due to any of an over-current, over-voltage,under-voltage, over-temperature, or under-temperature condition, forexample. Each fault condition may have a unique outcome in terms ofprecautionary measures or reactions under the control of motorcontroller 120, including, but not limited to, signaling warning codesvia meter 240 or warning lights on the LED 245 of the instrument panel,reducing motor 110 performance for continued drive operations, immediateshutdown, and the like. These fault conditions may occur at any vehiclespeed or under any operator condition where the motor controller 120detects one or more of the aforementioned fault conditions. In thisexample, motor controller 120 may take the precautionary action ofcommanding zero motor speed and then engaging the parking brake 180 (viaa brake control signal over signal line 185) within a short period orimmediately, and may disable motor 110 in some more extreme cases, forexample.

Another condition may occur if the key switch 220 is set to the OFFposition. Motor controller 120 may engage the electric brake 180 in anycase where the key switch 220 is set OFF, regardless of any other inputcondition, including vehicle 190 speed. This may provide a necessarysafety function as the key switch 220 is also the operator's onlyemergency stop switch on vehicle 190.

Other various embodiments enables the motor controller 120 to provide apedal up braking or neutral braking function based on given monitoredinputs, in order to detect an implemented desired braking condition whenthe brake pedal is not engaged. By pedal up braking, while the vehicleaccelerator pedal 170 is released, motor controller 120 may activelyimplement a regenerative braking situation to decrease vehicle 190 speeddown to a base speed of the motor 110. Thus, pedal up or neutral brakingmay represent an ability of the vehicle 190 to reduce the vehicle speedby a given amount per unit time, when neither the brake pedal 160 northe accelerator pedal (throttle) 170 is engaged, independent of vehicleslope (e.g., the slope of the vehicle on a hill or incline).

During normal operation of the vehicle 190, motor controller 120 maymonitor several operator inputs and vehicle conditions. For example,brake pedal position, accelerator pedal position, and actual motor speedmay be monitored by motor controller 120 to enable the implementation ofpedal up braking. When the accelerator pedal 170 and brake pedal 160 arenot engaged by the operator, and the vehicle 190's actual motor speed isdetermined to be in a given range, motor controller 120 may command themotor 110 to reduce speed by a given amount per unit time, for example.This reduction of motor speed for unit time may continue until the inputconditions or until the motor speed reaches a near zero speed condition.If a near zero motor speed is encountered, motor controller 120 maycommand the engagement of the automatic parking brake feature, reducingactual motor speed and stopping the vehicle 190. Accordingly, by virtueof automatically reducing the vehicle speed, even on a downhill slope,pedal up braking in accordance with various embodiments may provide anadditional measure of safety to the vehicle 190 operation.

Other various embodiments are directed to the implementation of a towmode. In the tow mode, motor controller 120 may be configured to limitthe maximum towing speed of vehicle 190 and to control motor 110. Thisis so that motor 110 neither consumes power nor generates power whilevehicle 190 is being towed.

The tow mode may be selected by setting the key switch 220 to the ONposition, the FNR switch 230 to the REV position, and selecting the TOWposition on the run/tow switch 210. As discussed above, the run/towswitch 210 may be located on the vehicle 190 at a place that isconvenient for towing, yet a location where the switch 210 may not beeasily activated from the operator's (or passenger's) position. This mayprovide reasonable assurance that the run/tow switch 210 will not bepurposefully or inadvertently cycled during normal driving evolutions ofthe vehicle 190.

One function of the tow mode may be to limit the vehicle 190 speed to,by way of example, 15 miles per hour, as specified by ANSI Z130.Selecting the key switch 220 to an ON condition enables the logic powerto the motor controller 120. Selecting the TOW position on the run/towswitch 210 may deactivate the electric parking brake 180, in order toprepare the vehicle 190 for towing. The service brake pedal 160 mayfunction normally while vehicle 190 is in the tow mode. In someconfigurations the FNR switch 230 may be set to a preferred position.

As logic supplied to the motor controller 120 is activated by a key ONcondition, motor controller 120 may monitor the actual towing speed ofthe vehicle 190. This may be accomplished via a feedback signal from themotor 110 or from a wheel 198 to the motor controller 120. The motorsignal may be provided by a suitable motor speed encoder, wheel speedencoder, sensor-less device and/or by monitoring the frequency orvoltage of the motor 110. Based on these inputs, motor controller 120may calculate that the vehicle 190 has reached a speed equal to, by wayof example, 15 MPH±some given error tolerance. Motor controller 120 maythen attempt to resist vehicle motion by commanding the vehicle 190, viamotor 110 and/or electric brake 180 to decelerate to, by way of example,15 MPH.

Another function of the tow mode may be to assist towing so as to have anegligible effect on the state of charge of the battery pack 130. Forexample, while the vehicle 190 is in tow, the motor controller 120 maymonitor current between the battery pack 130 and motor controller 120.Motor controller 120 may then command the motor speed or torque todeliver a net consumption of zero (0) amps battery current to offsetback EMF with forward EMF. Current is limited because the motorcontroller 120 can only turn the rotors so quickly. Although zero ampsconsumption may not be obtainable in actuality, the allowable error ofthe AC drive system 100 may facilitate the towing function, with thepositive and negative current to and from the battery pack 130 having anegligible effect on the battery pack 130's overall SOC condition.Further, while the vehicle is in the tow mode, controller 120 mayselectively activate the brake 180 to limit tow speed below apredetermined value, such as a predetermined motor revolutions perminute, such as 4800 RPM. Such a tow speed may be determined inaccordance with the ability of controller 120 to operate motor 110.

FIG. 4 is a block diagram illustrating a front wheel speed sensor inaccordance with various embodiments. Referring to FIG. 4, anotherembodiment may be directed to a front wheel speed sensor 510. The frontwheel speed sensor 510 may enable implementing one or both antilockbraking and traction control features on a vehicle 190 such as a golfcar or small utility vehicle. Traction control and antilock braking maylimit the ability for driven and braked wheels to slip with respect tothe road surface. Reduction in wheel slip may improve the control of thevehicle 190 by reducing the ability of the vehicle 190 to enter into askid. These features may greatly reduce vehicle stopping distance in theevent of a reduced friction road surface, such as wet grass, forexample. When a vehicle's road surface is a turf surface, tractioncontrol and antilock braking features may reduce the turf damage byreducing the amount of slip between the wheel 198 and the turf'ssurface.

Motor controller 120 may monitor the motor speed, which is proportionalto the driven wheel speed. Motor controller 120 may include storedpre-programmed data related to the vehicle 190's overall gear ratio,enabling the motor controller 120 to calculate the driven wheel speed,for example.

As shown in FIG. 4, a suitable wheel speed sensor 510 may be mounted toa hub of a non-driven and non-braked wheel 198 to measure the wheelspeed of a wheel that is not slipping relative to the road or turfsurface. The measurable data from the sensor 510 may be used to enablemaximum braking and/or acceleration without slipping. This data may becommunicated to the motor controller 120 via CAN bus 145, for example.Motor controller 120 may compare the calculated wheel speed of thedriven wheel 198 to the wheel speed input from the non-braked wheel 198.Motor controller 120 may then adjust the motor speed to match speed inan effort to reduce the error between the driven and non-driven wheel.Once the error has been reduced, motor 110 may accelerate or decelerateto match the actual motor speed to the commanded motor speed. Ifadditional errors are measured between the non-driven and driven wheelsby motor controller 120, motor controller 120 may further adjust themotor speed to reduce the given error within acceptable limits. Suchcontrol provides maximum braking or acceleration while minimizingslippage.

FIG. 5 is an exemplary block diagram illustrating a multiple or allwheel drive arrangement in accordance with various embodiments. AlthoughFIG. 1 illustrates other various embodiments in which motor 110 maydrive the rear wheels 198 via rear axle 192 and locking differential194, vehicle 190 could be configured to include a multiple or all-wheeldrive system. For example, a tandem motor arrangement or four separateAC motors 610A-D could be provided to power an individual orcorresponding wheel 198.

Driving two or more wheels of vehicle 190 independently may provideseveral advantages over the common solid axle conventionally used invehicles such as golf cars. For example, the differential carrier may beeliminated. Eliminating the differential 194 may eliminate mechanicallosses associated with mechanically differentiating wheel speed. Byproviding a sensor-based steering direction and then powering the wheelswith unequal torque or speed, the steering system may be assisted insteering the vehicle, possibly reducing the steering effort.Additionally, directly driving two wheels may provide the functionalityof a differential lock. This feature may generally provide foradditional tractive or braking effort. Further, with two-wheel orall-wheel drive, the solid beam axle 192 may be eliminated to facilitatean independent rear suspension. Accordingly, each wheel could be drivenby corresponding brushless AC motor 610A-D, each motor 610A-D providing3φ outputs. Further, each wheel could optionally include a correspondingspeed sensor 510 as shown in FIG. 4, for example. Alternatively, insteadof a 4-motor configuration, a tandem configuration is envisioned, whereone AC brushless motor (610A or 610B) drives the front wheels, andanother AC brushless motor (610C or 610D) drives the rear wheels.

By driving each wheel of vehicle 190 with two to four separate motors110, independent braking of the wheels may be conducted as needed toenhance traction during vehicle acceleration or braking and independentdriven wheel speeds may be measured with the front wheel sensor. Thesensor may be installed in the motor 110, for example. Additionally,such an arrangement may provide redundant operation in the event of ainoperability of a motor; the vehicle 190 may remain operational withonly motor system. Further, motor size may be reduced while providingequal or enhanced vehicle 190 performance. Reduced power levels may makedirect drive motors such as the brushless AC motor 110 described hereinmore technically feasible and economical. Finally, unsprung weight maybe reduced, thereby improving drive quality via the suspension system.

Accordingly, the use of an AC drive system in a vehicle such as a golfcar and/or a small utility vehicle may provide several distinctadvantages where precise position control is not a main objective and/orwhere an AC current source is not readily available, but may besimulated using a three-phase power inverter and a DC battery pack 130.

For example, the drive efficiency of selected AC motors may far exceed atypical series DC motors, or separately excited armature and field(shunt-type) DC motor. This higher efficiency may enable the vehicle 190to operate longer and to travel further on a smaller battery pack 130.

Additionally, peak motor torque may be available at zero motor RPM,thereby enabling the motor 110 to hold the vehicle 190 in place This mayprevent the vehicle 190 from moving in certain safety-criticalsituations for a long enough duration to enable the parking brake 180 tobe engaged and to avoid vehicle rollaway, for example.

Further, motor 110 may be controlled by motor controller 120 so as toproduce a control torque in either rotational direction. This may enablethe motor 110 use as a service brake, thereby eliminating the need for amechanical service brake, for example. Enabling the AC drive system 100to act as the vehicle service brake may convert a percentage of thevehicle 190's kinetic energy to electric potential energy, therebyproviding the ability to the charge the associated battery pack 130.Moreover, use of a motor 110 as a service brake reduces the heat energyproduced by using a mechanical service brake. The elimination of thisheat during service brake may enable the use of the lower temperatureplastics for body panels, components and wheels on the vehicle 190, forexample. Still further, a smaller, lighter motor may be used due to thehigh efficiency of brushless permanent magnets or induction motors, ascompared to series or shunt-type DC motors.

The description herein is merely exemplary in nature and, thus,variations that do not depart from the gist of that which is describedare intended to be within the scope of the disclosure. Such variationsare not to be regarded as a departure from the spirit and scope of thedisclosure.

1. A drive system for a vehicle, comprising: a motor for providing adrive torque to the vehicle via an output shaft; an electricallyactuated brake mounted to the output shaft for providing a brakingtorque to the output shaft; and a controller that receives a batteryvoltage input, a throttle pedal position input, a brake pedal positioninput that indicates a position of a brake pedal, a key switch input, aforward/neutral/reverse (FNR) input, and a full-stroke input thatindicates a full-stroke position of the brake pedal, the controllergenerating a drive signal for the motor based on the inputs; wherein thecontroller communicates a signal to the electrically actuated brakebased on at least one of the brake pedal position input and thefull-stroke input.
 2. The drive system of claim 1 wherein the motorincludes one of an induction motor and a permanent magnet motor.
 3. Thedrive system of claim 2 wherein the motor includes a wound stator and apermanent magnet rotor.
 4. The drive system of claim 1 wherein thecontroller further includes a media drive for receiving removablestorage media including Compact Discs (CDs), Digital Versatile Discs(DVDs), magnetic media, and memory cards.
 5. The drive system of claim 1wherein the controller further receives a throttle enable input.
 6. Thedrive system of claim 1 wherein the controller further generates awarning signal.
 7. The drive system of claim 1 wherein the controllerfurther generates a status signal that is communicated to a display. 8.The drive system of claim 1 further comprising a rechargeable batteryfor providing the controller with a source of electrical energy whereinthe rechargeable battery type includes one of lithium ion, nickelcadmium, nickel metal hydride, and lead-acid.
 9. The drive system ofclaim 8 wherein the motor controller recharges the rechargeable batterywith energy received from the motor.
 10. The drive system of claim 9wherein the motor controller determines a percentage of the energy toprovide to the rechargeable battery based on battery pack type, batterypack age, and rate of energy consumption.
 11. The drive system of claim1 wherein the motor controller further includes a communication businterface for communicating data.
 12. The drive system of claim 11further comprising a battery charger that includes a secondcommunication bus interface for communicating a battery state of charge(SOC) with the communication bus interface of the controller.
 13. Thedrive system of claim 1 further comprising a locking differential thatreceives and redirects the drive torque to a pair of axles.
 14. Thedrive system of claim 13 wherein the locking differential locks andunlocks in accordance with a differential control signal that isgenerated by the controller.
 15. The drive system of claim 1 furthercomprising a plurality of wheel speed inputs and wherein the drivesignal is further based on the wheel speed inputs.
 16. The drive systemof claim 15 wherein the controller includes at least one of an antilockbraking system and a traction control system that receive the wheelspeed inputs and limit acceleration and deceleration of the motor. 17.The drive system of claim 16 wherein the traction control system limitsthe acceleration and deceleration based on comparing wheel speed inputsassociated with a respective driven wheel and a non-driven wheel. 18.The drive system of claim 1 comprising a second motor for providing asecond drive torque wherein the motor controller communicates a seconddrive signal with the second motor and wherein the second drive signalis based on an operating condition of the motor.
 19. A drive system fora vehicle, comprising: a motor for providing a drive torque to thevehicle via an output shaft; an electrically actuated brake mounted tothe output shaft for providing a braking torque to the motor shaft; anda controller that receives a battery voltage input, a throttle pedalposition input that varies in accordance with a position of the throttlepedal, a brake pedal position input that varies in accordance with aposition of the brake pedal to indicate a commanded vehicle decelerationrate, a key switch input, a forward/neutral/reverse input, and a fullstroke input indicative of whether the brake pedal has been depressed toa parking brake position, the controller generating a drive signal forthe motor based on the inputs; wherein the electrically actuated brakeis operated to effect a parking brake function preventing rotation ofthe output shaft when the full stroke input communicates that the brakepedal has been depressed to the parking brake position.
 20. A drivesystem for a vehicle, comprising: a motor for providing a drive torqueto the vehicle via a shaft; an electrically released brake for providinga braking torque to the shaft; a controller that receives a batteryvoltage input, a throttle pedal position input that varies in accordancewith a position of the throttle pedal, a brake pedal position input thatvaries in accordance with a position of the brake pedal to indicate acommanded vehicle deceleration rate, a key switch input, aforward/neutral/reverse input, and a full stroke input indicative ofwhether the brake pedal has been depressed to a parking brake position,the controller generates a drive signal for the motor based on theinputs, wherein the controller communicates a signal to actuate theelectrically released brake to effect a parking brake functionpreventing rotation of the shaft when the key switch input indicates anOFF condition.
 21. The drive system of claim 20 wherein the controllersends an emergency brake control signal to actuate the electricallyreleased brake to effect an emergency brake function stopping rotationof the brake when the key switch input indicates an OFF condition andthe vehicle is moving.
 22. The drive system of claim 20 wherein thecontroller sends a parking brake control signal to actuate the brake toeffect a parking brake function preventing rotation of the motor shaftwhen the key switch input indicates an OFF condition and the vehicle isstopped.
 23. The drive system of claim 20 wherein the controller appliesthe electrically released brake regardless of any input other than thekey switch input.
 24. The drive system of claim 19, wherein the parkingbrake position comprises depression of the brake pedal to within apredetermined range of a maximum brake pedal depression position.